The Great Mimicker: Acute Obstructive Uropathy as a Rare Manifestation of Long-Standing Pseudomyxoma Peritonei.

Pseudomyxoma peritonei (PMP) is a rare clinical entity characterized by the accumulation of mucinous fluid within the peritoneal cavity. While often indolent, it can lead to severe mechanical complications. This case describes an elderly patient with advanced PMP presenting with acute obstructive uropathy, highlighting the complexity of managing frail oncologic patients. An 83-year-old female with a history of ovarian cancer and PMP (previously treated with cytoreductive surgery and HIPEC (hyperthermic intraperitoneal chemotherapy)) presented with a two-day history of right-sided flank pain, abdominal distention, and severe constipation. Laboratory results showed leukocytosis (13,790/µL) and elevated C-reactive protein (169 mg/L). A CT scan revealed progression of calcified peritoneal implants and a large epigastric mass causing extrinsic compression of the right ureter, leading to severe ureterohydronephrosis (7 cm). Despite the obstruction, renal function was preserved (creatinine 0.73 mg/dL). Due to her frailty and personal preferences, the patient declined invasive urinary diversion. She was managed conservatively, remained clinically stable, and was discharged with outpatient follow-up. PMP symptoms often mimic benign gastrointestinal issues, such as constipation. In elderly patients, the decision between aggressive intervention and conservative care is challenging. This case highlights the value of shared decision-making in advanced oncology; when renal function is stable, this model allows for a non-invasive approach that, beyond being a viable clinical alternative, stands as the best path to honor patient autonomy and optimize quality of life. Clinical vigilance is crucial in PMP, as nonspecific symptoms may mask serious obstructive complications. Individualized, patient-centered care is essential when balancing the risks of surgical intervention against conservative management in advanced oncology.